1. Field of the Invention
This invention relates to drilling machines used for drilling bores into terrain, especially but not exclusively for investigating the terrain and recovering samples.
2. Review of the Art
An example of such a machine is described in U.S. Pat. No. 4,303,130 of A. Bonca. Primary features of machines of this type are the provision of a drilling boom, and means to position and support this boom in alignment with a bore to be drilled. The drilling boom supports a drilling head for longitudinal movement along the axis of the boom, the drilling head including a motor, usually hydraulic, for rotating a drilling tube which passes through the head. The boom has an extension supporting tackle for handling extension tubes as these are added to the end of a string of drill tubes as drilling progresses, or as tubes forming part of the string are withdrawn from the bore. The boom is supported on a base mounted on a suitable support or vehicle, which in the case of the above patent is an all terrain vehicle.
Booms for such drills are typically fabricated by welding from steel sections, with machined ways for guiding the drill head, which must be maintained in good alignment with the boom despite the transmission through it of considerable torsional, longitudinal and lateral forces. Such booms have as a result been expensive to fabricate, difficult to maintain in alignment, massive, and bulky, particularly in view of the boom extension. Although the boom extension can in some cases be dismantled for transportation of the unit, time is then lost in reassembling the boom extension before the drill can be used, and it may be difficult or impossible to deploy the drill in confined spaces.